Compile samples and integration tests with Java 8

Update the samples and integration tests to use Java 8. There's no
specific reason to keep them on Java 6 and it helps keep Eclipse happy
if we upgrade.

spring-boot-samples/spring-boot-sample-hypermedia-gson/pom.xml

@@ -13,7 +13,6 @@
 	<description>Spring Boot Hypermedia GSON Sample</description>
 	<properties>
 		<main.basedir>${basedir}/../..</main.basedir>
-		<java.version>1.7</java.version>
 	</properties>
 	<dependencies>
 		<dependency>

spring-boot-samples/spring-boot-sample-hypermedia-jpa/pom.xml

@@ -13,7 +13,6 @@
 	<description>Spring Boot Hypermedia JPA Sample</description>
 	<properties>
 		<main.basedir>${basedir}/../..</main.basedir>
-		<java.version>1.7</java.version>
 	</properties>
 	<dependencies>
 		<dependency>

spring-boot-samples/spring-boot-sample-hypermedia-ui/pom.xml

@@ -13,7 +13,6 @@
 	<description>Spring Boot Hypermedia UI Sample</description>
 	<properties>
 		<main.basedir>${basedir}/../..</main.basedir>
-		<java.version>1.7</java.version>
 	</properties>
 	<dependencies>
 		<dependency>

spring-boot-samples/spring-boot-sample-hypermedia/pom.xml

@@ -14,7 +14,6 @@
 	<properties>
 		<main.basedir>${basedir}/../..</main.basedir>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-		<java.version>1.7</java.version>
 	</properties>
 	<dependencies>
 		<dependency>